Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
A number of diagnostic methods have been developed to evaluate physiological conditions of a person by detecting and/or measuring one or more analytes in a person's blood or other bodily fluids or tissues. The one or more target analytes could be any analytes that, when present in or absent from the blood, or present at a particular concentration or range of concentrations, may be indicative of a medical condition or health state of the person. The one or more target analytes could include enzymes, reagents, hormones, proteins, cells or other molecules, such as carbohydrates, e.g., glucose.
Interest in measuring the binding interactions between antibodies and their specific antigens has resulted in the application of a broad array of technologies to the development of immunodiagnostics. Because of its high sensitivity, fluorescence-based diagnostic assays based on Forster Resonance Energy transfer (FRET) have received considerable attention and have been broadly applied in biology and chemistry to obtain information about proteins and other biological molecules. Such assays are divided into two categories: homogeneous and heterogeneous, the latter involving physical separation of the assay mixture before detection while the former requires no separation steps. Most fluoroimmunoassays are heterogeneous and are often competitive assays in which a fluorescent labeled antigen (or antibody) completes for binding with an unlabeled antigen (or antibody). In such assays, the fluorescent labeled species are referred to as the tracer, and the unlabeled species are the analyte. Depending on the assay being performed, the analyte can be either an antigen or an antibody. After removal of unbound analyte and tracer, the signal intensity from the bound tracer is inversely proportional to the analyte concentration in the original solution.